Stabilizing the Deep Sodiation Process in Layered Sodium Manganese Cathodes by Anchoring Boron Ions

摘要

Advanced high-energy-density sodium-ion batteries (SIBs) are inseparable from cathode materials with high specific capacities. Layered manganese-rich oxides (NaxMnO2, 0.6 <= x <= 1) are promising cathode materials owing to their ease of intercalation and extraction of a considerable amount of sodium ions. However, lattice interactions, especially electrostatic repulsive forces and anisotropic stresses, are usually caused by deep desodiatin/sodiation process, resulting in intragranular cracks and capacity degradation in SIBs. Here, boron ions are introduced into the layered structure to build up BOMn bonds. The regulated electronic structure in Na0.637B0.038MnO2 (B-NMO) materials inhibits the deformation of MnO6 octahedra, which finally achieves a gentle structural transition during the deep sodiation process. B-NMO electrode exhibits a high capacity (141 mAh g-1) at 1 C with a capacity retention of 81% after 100 cycles. Therefore, anchoring boron to manganese-rich materials inhibits the detrimental structural evolution of deep sodiation and can be used to obtain excellent cathode materials for SIBs. @@@ The boron anchoring strategy in which inserting boron atoms into interstices between transition metal oxide layers has been proposed and implemented. Benefiting from easing anisotropic strains and reducing interlayer gliding during the deep sodiation process, the (Na0.637B0.038MnO2) B-NMO cathode material shows a remarkable specific capacity in the continuous cycling in sodium ion batteries.image

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